Document Type

Honors Thesis

Major

Biochemistry, Molecular & Cellular Biology, and Microbiology

Advisor(s)

Julie A. Gosse

Committee Members

Robert Glover, Samuel T. Hess

Graduation Year

May 2023

Publication Date

2025

Abstract

Cetylpyridinium chloride (CPC) is a cationic quaternary ammonium antimicrobial used widely in personal care and food products, despite the lack of literature assessing its eukaryotic toxicology. It is necessary to weigh the risk-to-benefit ratio of this antimicrobial agent. Mast cells (MC) are key players in the immune system, and their immune response degranulation is the release of effector compounds such as histamine. The degranulation signal transduction pathway depends upon on a series of molecular events: antigen binds to IgE receptor FcRI, triggering a cascade of tyrosine (Y) phosphorylation via Src-family kinases Lyn and Syk, leading to the enzymatic cleavage of the key eukaryotic membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP2), generating IP3 which binds its receptor on the endoplasmic reticulum, inducing calcium mobilization, leading to downstream degranulation. Previous work in our lab shows CPC inhibits degranulation, disrupts calcium mobilization, and interferes with PIP2. Evaluation of upstream events, including Y phosphorylation and PIP2-interference, are needed for detailing biochemical mechanisms of CPC toxicity. Enzyme-linked Immunosorbent Assay (ELISA) and Western blotting (WB) both show that CPC inhibits antigen-stimulated Syk phosphorylation. Our data to date indicate that CPC, conversely, does not affect tyrosine phosphorylation of Lyn, which contains both positive- and negative-regulatory tyrosine phosphorylation sites. However, moderate antigen dose conditions suggest a CPC-induced dysregulation of Lyn Y508, the inhibitory Y. Molecular Dynamics software GROMACS found that divalent cation Ca2+ bridges PIP2 lipid self-clustering and disrupts attractive forces between PIP2 and positively chargedamino acids in protein. These findings contribute to pin-pointing the mechanism underlying CPC disruption of immune cell function.

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